Oscillograph device



Oct. 25, 1938. R. ANDREU 2,134,094

OSCILLOGRAPH DEVICE Filed May 2l, 1956 INVENTOR Aober Andr/eu ATTORNEY Patented Oct. 25, 1938 fil HCE OSCILLOGRAPH DEVICE Robert Andrieu, Berlin, Germany, assigner to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H., Berlin, Germany, a corporatien of Germany Application May 21,

In Germany 3 Claims.

This invention is concerned with a circuit organization for cathode ray or Braun tubes for receiving television or video signals. According to the form of the invention herein to be described,

the cathode ray or so-called Braun tube is ener-v gized or fed with a radio-frequency voltage which is modulated in accordance with the shading value of picture units or points.

According to this invention, the circuit of the control grid of the cathode ray tube contains a parallel arrangement comprising a resistance and a condenser traversed by its plate current.

An exemplified embodiment of one form of the invention is schematically illustrated by Fig. 1 of the annexed drawing and the operation is further explained by the curves of Fig. 2.

Referring to the drawing, the cathode ray tube includes the glass envelope Ill having at one end a luminescent screen and at the opposite end a cathode II and an associated control grid or shield I2 which, in the instance here shown may be a Wehnelt cylinder. The anode I3 of the tube I0 is united with the positive pole of a D. C. source I4. Between the negative pole of the D. C. source I4 and the cathode or filament II is included a resistance I6 connected in parallel to a condenser I5. A D. C. source Il furnishes a constant negative potential for the shield or control grid I2, while a transformer I8 serves as the connecting means by which the cathode ray or Braun tube is fed with a radio-frequency voltage being modulated in accordance with the picture brightness or shading values, so that these signals are known as the video or image signals.

The cathode ray tube I0 is caused to operate (because of the application of potential II which could also be dispensed with if a suitable disposition and suitable dimensions of the control means I2 are chosen) atthe lower bend or knee of the characteristic which connects the anode current and the control-grid voltage. So far as the modulated RF voltage is concerned which is fed by way of the transformer I8, the discharge path cathode II and anode I3 therefore represents a rectifier stage with the result that the anode current and thus the stream of cathode-rays penetrating through the anode` aperture will be varied at the rhythm of the modulation impressed upon the radio-frequency voltage.

To explain the operation of the condenser I5 and the resistance I6 the assumption shall be made that across the secondary terminals of the transformer I8 a voltage having a time-shape as indicated by the curve ABCD arises (see Fig. 2). This voltage is distributed first in accordance with 1936, Serial No. 81,038 April 10, 1935 (Cl. TIS- 7.5)

the capacities over the path cathode II and control grid or shield I2 as well as condenser I5, and it then follows the dotted portion of the curve CE. The portion T indicates the time-constants of the mesh i5, I6. Hence, at the control grid arises the 5 voltage ABCE rather than the voltage ABCD in which the higher frequencies, which exist at the point of sudden irregularity to in particularly great volume, arise more strongly than the lower ones. The mesh or network comprising conl0 denser and resistor I5, I6 respectively, can be readily so proportioned that its time constant is somewhat greater than the period which corresponds to the highest frequency occurring in the picture, so. that the greater loss of high frequenl5 cies which is due, for instance, to the nite d1- mensions of the spots scanning the outgoing picture and re-creating the incoming image and also to capacity losses in the transmission path or medium, can be diminished or equalized.

Having now described the invention, what is claimed iszl. A cathode ray tube system comprising a cathode ray tube including a cathode, control electrode and anode electrodes, means for biasing the cathode of said tube with respect to the control grid thereof whereby said tube operates on the lower bend of its control grid .voltageanode current characteristic, a source of picture signals, means for impressing said signals onto the control electrode of said tube whereby said picture signals are directly detected by said tube, and a time constant circuit having a time constant greater than the highest modulation frequency of the picture signals, said time constant circuit 35 being connected in the cathode circuit of said tube for peaking the high frequency components of the picture signals.

2. A cathode ray tube system comprising a cathode ray tube including a cathode, control electrode and anode electrode, means for biasing said electrodes relatively to each other whereby said tube operates at a bend in its control grid voltage-anode current characteristic, a source of high frequency signals modulated in accordance 4 with picture signals, a time constant circuit for peaking the high frequency components of the picture, and means for impressing the high frequency modulated signals onto the control electrode of the tube whereby said signals are detected directly by said tube.

3. A cathode ray tube system comprising a cathode ray tube including a cathode, control electrode and anode electrode, means for biasing said electrodes relatively to each other whereby said tube operates at a bend in its control grid Voltageanode current characteristic, a source of high frequency signals modulated in accordance with picture signals, a time constant circuit for peaking the high frequency components of the picture, the secondary Winding of a high frequency trans former, a series electrical circuit comprising the control electrode of said tube, said secondary winding, a source of direct current electrical energy and the cathode of said tube, a primary Winding positioned cooperatively with respect to said secondary Winding and means for impressing the high frequency modulated signals onto said primary winding whereby said signals are detected directly by said cathode ray tube.

' ROBERT ANDRIEU. 

